I have multiple form application. Form 1 is Login form for user validation. Form1 goes to Form2(Menu form). Form 2 leads to Form3 which is only popupform and hides the form2 when it is open.Form 3 goes to Form 4. Now from Form4 ,with button click, I need to restore the Form2 without creating a new instance. I tried using singelton approach, getting error.Code as follows as described above.
我有多个表单应用程序。 表单1是用于用户验证的登录表单。 Form1转到Form2（菜单表单）。 表单2导致Form3仅弹出窗体并在窗体2打开时隐藏表单2.表单3转到表单4.现在，从Form4中，单击按钮，我需要还原Form2而不创建新的实例。 我尝试使用singelton方法，如上所述获取error.Code，如下所示。 Form1中： private void click_Click（object sender，EventArgs e） { if（（user.Text == username）&&（pswd.Text
Now i get the problem at the try statement ( int count =insert.......). The compailer says(when i push the buton on the form to save the values in textboxes) that it Failed to convert parameter value from a String to a Int32. code: private void button1_Click(object sender, EventArgs e) { string conString = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=C:\Users\Simon\Desktop\
现在我在try语句中得到了这个问题（int count = insert .......）。 比较器说（当我按下表单上的按钮来保存文本框中的值时）它无法将参数值从字符串转换为Int32。 码： private void button1_Click（object sender，EventArgs e）{ string conString = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=C:\Users\Simon\Desktop\save.mdb"; OleDbConnection empConnection = new OleDbConnection(co
If I am passing an object to a method, why should I use the ref keyword? Isn't this the default behaviour anyway? For example: class Program { static void Main(string[] args) { TestRef t = new TestRef(); t.Something = "Foo"; DoSomething(t); Console.WriteLine(t.Something); } static public void DoSomething(TestRef t) { t.Somethin
如果我将一个对象传递给一个方法，为什么我应该使用ref关键字？ 无论如何，这不是默认行为吗？ 例如： class Program { static void Main(string[] args) { TestRef t = new TestRef(); t.Something = "Foo"; DoSomething(t); Console.WriteLine(t.Something); } static public void DoSomething(TestRef t) { t.Something = "Bar"; } } public class T
I have written a smallish C program on Mac OSX that does the following steps: reads some input from stdin and stores input into memory. runs some computations and prints the output to stdio In between steps 1 and 2, I want to prompt the user and wait for some kind of keyboard input to signal "keep proceeding to step 2". The problem is that stdin has been redirected when the progr
我在Mac OSX上编写了一个小巧的C程序，它执行以下步骤： 从标准输入读取一些输入并将输入存储到内存中。 运行一些计算并将输出打印到stdio 在步骤1和步骤2之间，我想提示用户并等待某种键盘输入以发出“继续执行步骤2”的信号。 问题在于使用以下命令调用程序时stdin已被重定向： $ ./simple < input.in 我想在读取文件后将stdin重定向到键盘，我不知道如何执行此操作。 我尝试过使用 fclose(stdin); freopen("newin"
I have created a Windows Phone 8.1 XAML version of one of my existing app. I set the package version to 1.5.0.0, the created file is called SlovakApps.WindowsPhone_1.5.0.1_AnyCPU_bundle.appxupload. When I upload the file to Dev Center, a strange version is shown: Is this normal? Seems very strange to me. From Microsoft support: Yes this is very normal now when you are submitting a packag
我创建了一个我现有应用程序的Windows Phone 8.1 XAML版本。 我将包版本设置为1.5.0.0，创建的文件名为SlovakApps.WindowsPhone_1.5.0.1_AnyCPU_bundle.appxupload。 当我将文件上传到Dev Center时，会显示一个奇怪的版本： 这是正常的吗？ 对我来说似乎很陌生。 来自微软的支持： 是的，现在当您提交支持Windows Phone 8.1的软件包时，它会自动为您的更新生成一个版本号。 不要创建捆绑。 生成并上传.appxupload软
I'm working with the Classic K&R Book "The C Programming Language", Second Edition. I have this problem with the exercise in page 24 about Arrays. Exercise say (Copy and paste from PDF): #include <stdio.h> /* count digits, white space, others */ main() { int c, i, nwhite, nother; int ndigit[10]; nwhite = nother = 0; for (i = 0; i < 10; ++i)
我正在使用经典K＆R书“The C Programming Language”，第二版。 在第24页关于数组的练习中，我遇到了这个问题。 练习说（从PDF复制并粘贴）： #include <stdio.h> /* count digits, white space, others */ main() { int c, i, nwhite, nother; int ndigit[10]; nwhite = nother = 0; for (i = 0; i < 10; ++i) ndigit[i] = 0; while ((c = getchar()) != EOF) if (c >=
If C does not support passing a variable by reference, why does this work? #include <stdio.h> void f(int *j) { (*j)++; } int main() { int i = 20; int *p = &i; f(p); printf("i = %dn", i); return 0; } Output $ gcc -std=c99 test.c $ a.exe i = 21 因为您将指针的值传递给方法，然后将其解引用以获取指向的整数。 That is not pass-by-reference, that is pass-by-value as others s
如果C不支持通过引用传递变量，为什么这会起作用？ #include <stdio.h> void f(int *j) { (*j)++; } int main() { int i = 20; int *p = &i; f(p); printf("i = %dn", i); return 0; } 产量 $ gcc -std=c99 test.c $ a.exe i = 21 因为您将指针的值传递给方法，然后将其解引用以获取指向的整数。 这不是传递参考，就像其他人所说的那样，传递价值。 C语言是毫无例外地传递值。 将指针作为参数
I'm fairly new to programming. The the constant issue I keep facing when I try anything for myself in C based languages is the scope. Is there any way to use or modify a variable from within a different method or class? Is there also a way to do this without creating a new intance of a class or object? It seems to wipe the slate clean every time. Example, I'm setting up a console t
我对编程相当陌生。 当我用C语言为自己尝试任何东西时，我一直面临的问题是范围。 有什么方法可以在不同的方法或类中使用或修改变量吗？ 有没有办法做到这一点，而不创建一个类或对象的新实例？ 它似乎每次擦拭石板都很干净。 例如，我正在设置一个控制台文本游戏，并且我想要以特定的时间间隔向控制台写入不同的背景消息。 public static void OnTimedEvent(object scource, ElapsedEventArgs e) { if(Expositio
I'm looking for a clear, concise and accurate answer. Ideally as the actual answer, although links to good explanations welcome. This also applies to VB.Net, but the keywords are different - ByRef and ByVal . By default (in C#), passing an object to a function actually passes a copy of the reference to that object. Changing the parameter itself only changes the value in the parameter,
我在寻找一个清晰，简洁和准确的答案。 理想情况下，作为实际答案，尽管欢迎提供良好解释的链接。 这也适用于VB.Net，但关键字不同 - ByRef和ByVal 。 默认情况下（在C＃中），将对象传递给函数实际上将引用的副本传递给该对象。 更改参数本身只会更改参数中的值，而不会更改指定的变量。 void Test1(string param) { param = "new value"; } string s1 = "initial value"; Test1(s1); // s1 == "initial value"
Some papers on GHC runtime internals mention that it uses epoll/kqueue/poll to detect whether a file descriptor is ready to read/write. I can understand how it's done for socket I/O. But what about disk file access? The poll syscall doesn't work with ordinary files, only with socket I/O; true? The only option I can imagine here is using a thread pool for blocking syscalls, one thre
关于GHC运行时内部的一些论文提到它使用epoll / kqueue / poll来检测文件描述符是否准备好读/写。 我可以理解它是如何完成套接字I / O的。 但是磁盘文件访问呢？ 轮询系统调用不适用于普通文件，仅适用于套接字I / O; 真正？ 我能想象到的唯一选择是使用线程池来阻塞系统调用，每个线程请求一个线程... 在无螺纹的RTS中，整个运行时间将被阻塞。 在线程化的RTS中，它会通过线程池来执行安全的外部调用，所以功能不会被